As we approach the 15-year mark since the Fukushima Daiichi Nuclear Power Station (FDNS) disaster, brought about by Tokyo Electric Power Company (TEPCO) and the Japanese government, the government is still unable to revoke the Nuclear Emergency Declaration. Further, without knowing what will happen in the future, and with an exceedingly hazardous accident site that has absolutely no outlook for a final conclusion, the Kashiwazaki-Kariwa Nuclear Power Station is being restarted. This stance itself fully exposes the true nature of TEPCO, and despite its being a company that is essentially declaring itself to be extremely irresponsible, the government makes no attempt to regulate it.<\/p>\n
Childhood thyroid cancer in Fukushima Prefecture is at a level of several tens of times above normal incidence, but neither TEPCO nor the government recognize exposure to radiation as the cause. Whatever textbooks or papers you look at, however, all state that \u201cexposure to radiation is a definite carcinogenetic factor for thyroid cancer.\u201d There is no safe dose of radiation. As indicated by the \u201clinear no-threshold (LNT) model\u201d the risk increases in direct proportion to the radiation dose \u201cwith no threshold value,\u201d a risk thus being associated even at low doses. Moreover, the LNT model has been confirmed by epidemiological studies and is the basis of radiological protection.<\/p>\n
The cause of the high incidence of thyroid cancer after the Chernobyl nuclear accident was formally recognized as having been due to exposure to radioactive iodine around ten years after the accident occurred. This is also substantiated by Japanese \u201cspecialists\u201d led by Dr. Yamashita Shunichi, who published a paper (1)<\/sup> stating that thyroid cancer was seen in children born before the accident, but not in children born after the accident, by which time the radioactive iodine would have disappeared. Nevertheless, Dr. Yamashita and other researchers at Fukushima Medical University (FMU) say that the high incidence of the cancer is not due to exposure to radiation but is the result of high rates of detection using highly sensitive ultrasonography. Why was exposure to radioactive iodine recognized as the cause at Chernobyl but not at Fukushima?<\/p>\n \u00a0<\/p>\n Current status of the high incidence of thyroid cancer in Fukushima<\/strong><\/p>\n Up to the time of the meeting of the Fukushima Health Management Survey Oversight Committee in late November 2025, the number of people in which malignant or suspected malignant cancers had been detected was 361, and 303 operations revealed one person with a benign cancer (see Table 1<\/strong>). However, we have previously reported that the activities of the 3.11 Fund for Children with Thyroid Cancer (the Fund) revealed that omissions in the tally are inevitable in this survey system (2, 3)<\/sup>. It was discovered that 47 patients had been missed up to 2019 when FMU cross-checked their data with the National Cancer Registry, but no reports have been published since that time. As the Fund had independently identified an additional eight cases, the total number of cases were at least 415 persons.<\/p>\n Table 1. Thyroid Cancers Identified in the Fukushima Health Management Survey Thyroid Examination (Up to the Report of the Oversight Committee in November 2025)<\/p><\/div>\n What needs to be especially noted in the table is that 1) persons assessed as showing no abnormality even by the highly sensitive ultrasonography examination in the previous tests (two years prviously), were found to have cancers of 5.1mm diameter or more. These were especially numerous, 46.5%, in Round 2, showing that there are cancers with this high growth rate. 2) Thyroid cancer is a cancer that is generally more prevalent among females, and there are reports that show that the number of females is usually several times that of males among the age group targeted by the survey. In the case of Fukushima, especially up to Round 4, the proportion of males is high. This phenomenon of a high male rate was also seen at Chernobyl and is considered to be a characteristic of the effect of exposure to radiation. 3) The participation rate falls with each round, but the incidence rate falls in Rounds 2 and 3 and rises again from Round 4 (seven years after the accident). (Data for Round 6 is still incomplete.)<\/p>\n \u00a0<\/p>\n Controversy over the cause of the high incidence of thyroid cancer<\/strong><\/p>\n While there is no objection to the fact itself that there is a high incidence of thyroid cancer, there are three arguments regarding the cause.<\/p>\n Firstly, FMU points out, among others, that the estimated radiation dose in the 2020\/2021 report of United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR), which it has adopted, is low. It also notes that there is no correlation between the increasing number of cases with the exposure dose (the correlation with the estimated dose will be discussed in the next section), and that thyroid cancers increased during the first three years after the accident. FMU thus claims that the increase in thyroid cancers is attributed not to the effects of radiation exposure, but to the detection through screening using highly sensitive ultrasonography. The counterargument to this is that there are cases where the cancers have grown to a diameter of 5.1mm or more within two years. Moreover, if the highly sensitive ultrasonography has accelerated the detection of many cancers, then it is impossible to explain why the incidence rate continues to rise after the fourth round.<\/p>\n The Oversight Committee, as does FMU, denies the radiation effects, but differing from FMU, some members claim that \u201cthere is a possibility of overdiagnosis, whereby cancers are detected that will not lead to clinical symptoms or death in the future.\u201d While FMU and almost all members of the Oversight Committee deny overdiagnosis, some members are insisting that thyroid gland examinations in schools should be downsized or suspended to reduce the risk of overdiagnosis. No scientific evidence has been provided regarding overdiagnosis; on the contrary, the paper by Yamashita et al. cited above (1)<\/sup> provides evidence that overdiagnosis does not occur as the result of screening. However, as large parts of the media have uncritically disseminated the information about overdiagnosis, this has been very convenient for political pressure to shut down the thyroid examinations, bringing about a very stressful situation for patients.<\/p>\n At the same time, researchers other than those at FMU say that as the estimated exposure dose in the 2020\/2021 UNSCEAR report is an underestimate, and as there is correlation seen between exposure dose and thyroid cancer incidence, this indicates evidence that the cause of the cancers is exposure to radiation (4)<\/sup>.<\/p>\n \u00a0<\/p>\n Is it true that \u201cthere is no correlation between exposure dose and thyroid cancer incidence\u201d?<\/strong><\/p>\n FMU has conducted several analyses of the correlation between radiation dose and incidence rates using different methods. Especially with Round 2, while once obtaining a result that indicated a correlation, the correlation was made to disappear after changing the zoning method of the contaminated area, finally concluding that no correlation existed (5)<\/sup>. Summarizing the data from Round 1 to Round 4, the Thyroid Examination Evaluation Subcommittee, which conducts assessments of the thyroid examination as a subordinate organization of the Oversight Committee, concluded that \u201csince it cannot be recognized that there is any consistent relation (dose-response relationship) in which detection rate rises with increasing dose, the association between thyroid cancer and exposure cannot be recognized.\u201d (6)<\/sup><\/p>\n Fig.1<\/strong> shows the results of an analysis, using the case-control study method, on the examinations up to Round 5, which was submitted in November 2025 by the Evaluation Subcommittee. The objection that \u201cwhile the difference may not be significant, it would be more natural to see this as incidence rising as dose increases\u201d arose from a member of the Evaluation Subcommittee. What do you, the readers, think when you look at the figure? Denying that exposure to radiation is the cause is really quite unjustifiable.<\/p>\n Figure 1. Odds Ratio for Each Matching Model in Case Control Study within the Cohort and with Zone Exclusivity<\/p><\/div>\n \u00a0<\/p>\n Conclusion<\/strong><\/p>\n As the half-life of radioactive iodine, the cause of thyroid cancer, is eight days, it becomes impossible to measure its presence after six months. Children born after that have almost no iodine exposure, and thus if thyroid examinations are conducted on children born after the accident, as indicated at Chernobyl (1)<\/sup>, it should be possible to tell whether or not the thyroid cancers have increased due to the effect of the accident. Such a proposal has not been forthcoming from the Evaluation Subcommittee or the Oversight Committee. Despite the availability of a best path, it is very strange that it has not been chosen. And this is very similar to the idea that while a nuclear phaseout is the best way to eliminate nuclear power plant accidents, we are deceived into thinking that damage and suffering can be prevented by devising evacuation plans.<\/p>\n Reference materials<\/strong><\/p>\n <\/p>\n","protected":false},"excerpt":{"rendered":" By Sakiyama Hisako, Takagi School, 3.11 Fund for Children with Thyroid Cancer \u00a0 Introduction As we approach the 15-year mark since the Fukushima Daiichi Nuclear Power Station (FDNS) disaster, brought about by Tokyo Electric...<\/p>\n","protected":false},"author":2,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"footnotes":""},"categories":[24,78],"tags":[],"class_list":["post-9028","post","type-post","status-publish","format-standard","hentry","category-fukushima","category-radiation-exposure"],"acf":[],"_links":{"self":[{"href":"https:\/\/cnic.jp\/english\/index.php?rest_route=\/wp\/v2\/posts\/9028","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/cnic.jp\/english\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/cnic.jp\/english\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/cnic.jp\/english\/index.php?rest_route=\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/cnic.jp\/english\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=9028"}],"version-history":[{"count":8,"href":"https:\/\/cnic.jp\/english\/index.php?rest_route=\/wp\/v2\/posts\/9028\/revisions"}],"predecessor-version":[{"id":9080,"href":"https:\/\/cnic.jp\/english\/index.php?rest_route=\/wp\/v2\/posts\/9028\/revisions\/9080"}],"wp:attachment":[{"href":"https:\/\/cnic.jp\/english\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=9028"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/cnic.jp\/english\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=9028"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/cnic.jp\/english\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=9028"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}![\"\"](\"https:\/\/cnic.jp\/english\/wordpress\/wp-content\/uploads\/2026\/03\/T1_shibayama-sensei-e1774600095958.jpg\")
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